4.4.3. Plugin Descriptions

The following are descriptions of a few commonly installed Yum plugins:

presto (yum-presto)

The presto plugin adds support to Yum for downloading delta RPM packages, during updates, from repositories which have presto metadata enabled. Delta RPMs contain only the differences between the version of the package installed on the client requesting the RPM package and the updated version in the repository.

Downloading a delta RPM is much quicker than downloading the entire updated package, and can speed up updates considerably. Once the delta RPMs are downloaded, they must be rebuilt to apply the difference to the currently-installed package and thus create the full, updated package. This process takes CPU time on the installing machine. Using delta RPMs is therefore a tradeoff between time-to-download, which depends on the network connection, and time-to-rebuild, which is CPU-bound. Using the presto plugin is recommended for fast machines and systems with slower network connections, while slower machines on very fast connections may benefit more from downloading normal RPM packages, that is, by disabling presto.

refresh-packagekit (PackageKit-yum-plugin)

The refresh-packagekit plugin updates metadata for PackageKit whenever yum is run. The refresh-packagekit plugin is installed by default.

rhnplugin (yum-rhn-plugin)

The rhnplugin provides support for connecting to RHN Classic. This allows systems registered with RHN Classic to update and install packages from this system.

Refer to man rhnplugin for more information about the plugin.

security (yum-plugin-security)

Discovering information about and applying security updates easily and often is important to all system administrators. For this reason Yum provides the security plugin, which extends yum with a set of highly-useful security-related commands, subcommands and options.

You can then use either yum update --security or yum update-minimal --security to update those packages which are affected by security advisories. Both of these commands update all packages on the system for which a security advisory has been issued. yum update-minimal --security updates them to the latest packages which were released as part of a security advisory, while yum update --security will update all packages affected by a security advisory to the latest version of that package available.

In other words, if:

the kernel-2.6.38.4-20 package is installed on your system;

the kernel-2.6.38.6-22 package was released as a security update;

then kernel-2.6.38.6-26 was released as a bug fix update,

...then yum update-minimal --security will update you to kernel-2.6.38.6-22, and yum update --security will update you to kernel-2.6.38.6-26. Conservative system administrators may want to use update-minimal to reduce the risk incurred by updating packages as much as possible.

Refer to man yum-security for usage details and further explanation of the enhancements the security plugin adds to yum.